Calculation Object in Universe

Need some inputs on creation of a Variable at universe Level.We have two tables Say A and B , B table is a calendar and holds daily date and a indicator that it was a Business day or not ,with value Y or N.

Table A will have a date say load date and a serial number of the product. We are looking to have the output as Serial Number ,load date , Previous Business day in one table in Webi.

Not getting how to achieve this , something's but not achieving this .